We propose to study the influence of diets containing different amounts of Vitamin C on the age at incidence, percentage incidence, rate of progression of severity and mortality from spontaneous primary mammary carcinoma induced by the milk factor in virgin C3H/He inbred strain of mouse. This strain ordinarily experiences an incidence of 60 to 80% breast cancer in virgins at age about 11 months. The experiment will be conducted in two stages. The first stage is to gather information for the design of a good second stage for the study of the above objectives. The second stage will study six different concentrations of vitamin C in a feed which is otherwise the same in 90% of its composition. The remaining 10% will consist of vitamin C, glucose and cellulose in such proportions that the vitamin C content varies from 1 to 10% of the total while the caloric content of the feed remains constant. Urine, serum, and leucocytes will be analyzed for vitamin C and plasma for corticosterone.